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Why are my cut stars a disaster


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#1 royster

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Posted 09 January 2021 - 01:28 AM

I have been on a star making frenzy lately. I dumped many, many batches 😂. After a lot of trial and error im having success with rolled stars and pumped stars using a 3/8 star plate from woodys.

For some reason when i try to cut stars i get bad results with charcoal compositions, my last attempt was willow diadem. Got the comp all mixed up, sprayed 75/25 water isopropyl alcohol till it was doughy, cut them up, they dried. When i test it it emits some titanium spark for a second then it just look like a hot piece of charcoal, and it stays lit for a while. I had a bunch of comps do that.

I had 2 successful batches of cut stars and with both i didnt use any water, just straight up denatured alcohol 🤷‍♂️. Every tutorial i read or watch everyone is using water or water and alcohol so im obviously doing something wrong i just cant figure out what it is. Any insight or help will be greatly appreciated.

#2 Arthur

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Posted 09 January 2021 - 04:38 AM

All comps fail if they are not properly dried, that's a lot dryer than "feels crisp on the outside" 

 

First try to make a moderate quantity -say 100g and weigh them carefully every day, they are not dry til they have kept the same weight for a day or three. It's very easy to have a dry outside but a damp inside on a star.



#3 Carbon796

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Posted 09 January 2021 - 09:08 AM

WD won't display properly if it's not moving through the air. The same goes for a lot of charcoal based comps. And as above, they need to be dry.

#4 justvisiting

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Posted 09 January 2021 - 11:50 AM

Like they said! I make my willow diadem cut stars by the bag method. I've used hot water, cold water, too much water, and never failed to make good stars. Yours may be just fine. I would never use alcohol for charcoal stars. Water has always worked, and alcohol could mess with the binding. The problem may not be apparent until a hard break is used.

 

Another thing newer pyros may not know is that charcoal stars should not be force-dried. Ideally, they are dried with cool, circulating air. Otherwise, they may never dry properly. One commonly used test is to put the stars into a sealed bag in the sun and see how much condensation forms inside the bag. A tiny bit is normal. Another common test is to split a star in half and scratch the inside. If the scratch is white, the star is dry. If it's blackish, it's not dry enough yet. 



#5 MadMat

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Posted 09 January 2021 - 03:33 PM

I will concur With Justvisiting. If you try to dry charcoal stars too quickly, a skin can form on the outside that will seal moisture in the middle of the star. This is commonly known as driven in moisture. What you describe as a glowing coal left behind, certainly sounds like your stars aren't dry all the way through. I also agree with Carbon796 most charcoal stars burn VERY differently flying through the air as opposed to being still. I wouldn't give up on your stars just yet. Continue to let them sit out in a warm and dry area. Back when I was a newbie, my first batch of cut charcoal stars took two weeks before they were dried out. Too bad I had thrown out most of them before finding this out! One thing you can do is weigh out your stars. After 3-4 days re-weigh them and see if they have lost any weight. If so, continue to check the weight every couple days until they stop losing weight.



#6 justvisiting

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Posted 09 January 2021 - 03:48 PM

Another thing: folks that have driven in the moisture have reported success in salvaging them with MORE water. Yes, they moisten the outside and seal them up, and the moisture inside gets a pathway back out, once the 'skin' is softened back up. Then they are dried normally. I've never done it.



#7 Arthur

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Posted 09 January 2021 - 04:36 PM

Cut stars need a lot of moisture to cut well, then that moisture has to go away, which takes time and maybe gentle heat or reduced humidity. Make a batch and leave them to dry in a dry place for a month, just make stock stars. Pick a style and make say five sizes then leave them for a month in vented containers. Use reusable silica gel packs if necessary.



#8 Richtee

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Posted 09 January 2021 - 05:25 PM

I will concur With Justvisiting. If you try to dry charcoal stars too quickly, a skin can form on the outside that will seal moisture in the middle of the star. This is commonly known as driven in moisture. 

Heh... In the sausage world it’s called “case hardening”. Patience IS a virtue.

 

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  • MadMat likes this
I like smoke! On food or in the air equally well.

#9 royster

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Posted 11 January 2021 - 12:54 PM

Richtee those sausages are looking amazing.

So yes i was force drying them, they seemed bone dry but performed poorly, but today after sitting more they perform better. I think its something to do with the stars expanding a little, they are actually really good now.

Yuuuup i need to stop using denatured alcohol now that i can find isopropyl alcohol. 25/75 water/denatured alcohol did work for stars, it dried fast and binded well but it does make things burn a lot faster. Thats something i also noticed with my nozzless 4 oz rockets, if i use too much denatured alcohol to granulate the fuel it becomes too hot for even nozzleless.

Ill keep denatured alcohol for lift charge and start embracing the traditional 75/25 water isoalcohol. Launched first successful shell yesterday using visco as time fuse, the first 2 didnt light up, had to go look for the shells for an hour 🤣

#10 Richtee

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Posted 11 January 2021 - 04:59 PM

Richtee those sausages are looking amazing.
. Launched first successful shell yesterday using visco as time fuse, the first 2 didnt light up, had to go look for the shells for an hour

Thank ya sir.

 

And visco works well for time fuse, but you gotta split it with a razor blade. Even better dip the split end in NC/BP mill dust or fines. Of course you can’t count the split end for timing purposes. Here’s the end of one of my .450 Bushmaster shells...

 

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Edited by Richtee, 11 January 2021 - 05:08 PM.

I like smoke! On food or in the air equally well.




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